Adjustable slit



3 J 0 2 P? 1 ms SEARCH m P 5, 1961 NsM. RASKHODOFF ETAL 2,998,730

ADJUSTABLE SLIT Filed Aug. 50, 1960 '3 m.

32 3e 37 33 3s 43 5| I8 /////%W//////// 7 23 |(O 29 SI/ 24 I3/ 20 I2 2|15 22 INVENTORQ NICHOLAS M. RASKHODOFF ARTHUR G. LOWELL BY 1%.! -M g/sdATTORNEY United States Fatent O 2,998,730 ADJUSTABLE SLIT Nicholas M.Raskhodofi, Cheverly, Md., and Arthur G. Lowell, Washington, D.'C.; saidLowell assignor to the United States of America as represented by theSecretary of the Navy Filed Aug. 30, 1960, Ser. No. 53,018 3 (Claims.(Cl. 74-89) (Granted under Title 35, US. Code (1952), see. 266) Theinvention described herein may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

The present invention is directed to an optical slit device and moreparticularly to the drive mechanism for an adjustable optical slitdevice.

Heretofore optical slits of small magnitude have been fixed such thatthey are not adjustable relative to each other. These slits are made bypiercing or punching a piece of material to make the slit. Other slitshave been made which are adjustable; however, these slits are large inphysical size and the adjustments cannot be made with accuracy in themicron adjustment region. In the stationary slit type, obviously, theslit is not adjustable and with the prior art adjustable slits, anydesired time adjustment cannot be made.

The present invention overcomes the disadvantages of the prior devicesby providing a small device capable of making an adjustable slit havinga width of about 0.004 inch, adjustable from zero to 0.0005 inch withone revolution of a worm drive means in an adjustable means andmaintaining the slit jaws in parallel alignment. The fine adjustment andparallelism are maintained by use of a stationary jaw and a movable orslidable jaw. The movable jaw is driven relative to the stationary jawby two cams which rotate against the back of a sliding block or elementto which one jaw is secured. The two cams are rotated by worm gearswhich drive the slide element relative to the stationary jaw in order tomake slits of different width.

It is therefore an object of the present invention to provide a smallsized, simple means of making slits which may be adjusted to obtaindesired widths of varying degree.

Another object is to provide a simple, accurate device for maintainingparallelism between surfaces adapted to form a slit.

Other and more specific objects of the invention will become apparentupon a careful consideration ofthe following detailed description whentaken together with the accompanying drawing in which:

FIG. 1 is a top-side plan view of the device shown in perspective,

FIG. 2 is a view shown in perspective with portions cut away to moreclearly illustrate the operating parts; and

FIG. 3 is a cross sectional view taken along the axis through the lengthof the device.

The present invention is directed to a very compact, adjustable slitdevice capable of attaining an extremely minute motion, forward orbackward, for the movable jaw of the slit assembly to provide a slitwidth adjustment of 0.0001 inch or less. This adjustment is accomplishedby means of a worm-worm gear drive, with an extremely low rise camsecured to the worm gear. The drive comprises two identical drive meanslocated beside each other in parallelism such that each of the cams onthe worm gear contact the back face of a slide member to which one jawis secured for movement therewith. The cams are held in constant contactwith the slide member by means of a tension spring. Thus the tensionspring insures that the slide member will contact the cams at all icetimes when moving in either direction. In addition to having two drivingcams, the slide is guided by a springloaded ball assembly which exerts adownward pressure onto the slide and rides in a centering groove in thetop surface of the slide. For the purposes of explanation, the slidewith one jaw secured thereto may be referred to as the slidable, movableor adjustable jaw.

Now referring to the drawing, there is shown by illustration a preferredslit assembly which includes a rectangular base 10 having one end 11thicker than the remainder with the surface of the base from the thickportion to the end being smooth and flat. The thick end 11 is machinedfrom the back side to include a space or hous ing in which a gear driveassembly is assembled. The drive assembly includes a pair of elongateddriving worms 12 and a pair of cylindrical driven worm gears 13 each ofwhich are secured in parallel relationship. Each of the worm gears areprovided with aslowly rising cam 14 secured to the outer surface thereofand having a greater diameter than the worm gears. The driving worms aresmaller at one end 15 than the diameter across the worm at the threadedportion and larger at the opposite end 16 such that the ends of each ofthe worms serves as a shaft with the smaller end 15 passing through ahole 17 in the base. The upper portion 16 of the driving worms.

have a knurled head 18 secured thereto which serves asthe control knobfor rotating the worm. Each driving worm is provided with a groove 21near the lower end. on the portion extending beyond the base withinwhich a bowed or spring type retaining ring 22 is inserted forpositioning the drive worm in the base and for eliminating end play. Thedriven worm-gears are supported by a shaft 19 such that the driven gearsare parallel to each other and in proper position for their threads toengage the driven worm. The shaft 19 is secured in place by a lock screw20 which screws through the housing to con tact the shaft.

The slit forming jaws are formed on similar steel blocks 23 and 24 whichare not as wide as the base member 10. One of the ends of each of theblocks 23 and 24 is formed at an angle with the end sloping from theupper side toward the bottom. The end of each of the blocks has a smoothedged member 25 such as a razor blade secured thereto by a plate 26 andbolts 27 which screw into the upper surface of the plates 23 and 24. Oneof the blocks is secured to the base by bolts 28 to provide a stationaryslit forming surface or jaw. The other block is secured to the baseslidable thereon and adjustable relative to the stationary block to forman adjustable slit forming member on the upper side of the block suchthat when assembled the angle at the end of each block diverges towardthe base member. The base member is cut away to form an opening 29therethrough for the purposes of admitting light to the slit formed bythe two jaws. The stationary block is secured to the end of the baseremoved from the worm-gear drive assembly with the slit torming memberfacing toward the gear drive assembly.

The slidable block or adjustable slit jaw 24 is provided with anelongated slot or groove 31 along the linear axis and the slidable blockis secured on the base between the stationary jaw and the worm-geararrange ment with the back end of the block in contact with the cams onthe worm gears. The adjustable slit jaw is secured to the base by abridge 32 which includes a retainer housing 33 at its center whichextends perpendicular to the base. The retainer housing contains acaptivated stainless steel ball 34 which is retained in the housing atthe bottom and is backed by a nylon centering washer 35 which centersthe bearing and a spring 36 which applies pressure on the steel ball.The spring is held in the retainer housing by a cap 37 secured in the 3housing. The bridge is secured by bolts 38 such that the steel ballrides in the groove 31.

A tension spring 41 is secured to the slidable jaw along the axisthereof by a pin 42 and to the center of the raised portion of the baseor housing which houses the gears by a screw 43. The tension springserves to maintain the back face of slidable jaw in contact with the twocams secured to the worm gear. The stainless steel ball bearing againstthe top of the slidable jaw maintains proper pressure contact betweenthe base and the slidable jaw thereby eliminating excessive frictionduring adjustment of the slidable jaw. Rotation of the knurled head onthe worm rotates the Worm gear which in turn rotates the cams againstthe back face of the slidable jaw. The knurled head is provided with asmall hole 5'1 within which a small pin 52 may be inserted to aid inturning the drive for minute adjustments. The spring will maintain theslidable jaw in contact with the cam such that the slidable jaw willmove in either direction depending on the rotation of the cam.

The particular slit device illustrated is constructed on a stainlesssteel base 95 inch wide, 3% inches in length and has a height varyingfrom ,4 inch to a minimum of inch at the slit. The slit is inch inlength and adjustable for a width of 0.004 inch with a fine adjustmentfrom zero to 0.0001 inch. The gear ratio between the worm and worm gearof 32:1 and a cam rise of 0.004 inch in 90 degrees moves the cam 11%degrees with one revolution of the driving worm. Thus the cam will movethe adjustable jaw 0.0005 inch with one revolution of the driving worm.With only a very small rotational movement of the cam, the slit widthcan be adjusted for very small changes between zero and 0.0005 inchwithin the movement resulting during one revolution of the driving worm.

It is important that the elements forming the slit be very smooth alongtheir slit surfaces therefore it is important that the two surfaces beground and honed or made with perfectly smooth surfaces. Otherwise theslit face surfaces may have a wavey face which would not permit the finenarrow slit width over the entire length. Any roughness of the surfacewould have a deleterious effect on any spectrum or photo taken throughthe slit.

In operation, the relative parts are assembled onto the base and theslit width is adjusted for the correct opening by rotation of the driveworms. Since the device comprises two worm drives each of the drivesmust be rotated simultaneously to slide the slidable jaw relative to thestationary jaw in order to more accurately position the slidable jaw inparallelism with the stationary jaw. The steel ball retained in thebridge rides in the groove in the upper surface of the slidable jaw toallow for a pivotal and slidable movement of the slidable jaw. If theslidable jaw were secured for strictly a forward and backward motion,there is a possibility that the two jaws of the slit would not beparallel. Likewise, this is true, if there is only one drive means formoving the slidable jaw. The use of two drive means and the steel ballwhich permits a pivotal as well as a slidable movement provides a devicein which the slidable jaw can be accurately aligned for parallelism withthe stationary jaw. Since the cams on each of the drive means and theradio of the drive worm to the driven worm gear are the same for each ofthe drive means, the same rotational movement for each drive worm wouldresult in a parallel movement of the slidable jaw provided the jaws areparallel at the beginning of the adjustment.

The small size of the adjustable slit device makes it useful with avacuum spectrograph wherein the slit can be adjusted and then enclosedin the vacuum system in the light path without the use of any bulky slitholders. Obviously, the device could be used for other purposes and alsothe size of the device could be enlarged Without departing from theinvention.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. An adjustable slit device which comprises an elongated base, astationary jaw secured at one end on the upper surface of said base, anaxially aligned linear slidable jaw slidably and pivotally mounted onthe upper surface of said base relative to said stationary jaw, a groovein the upper surface of said slidable jaw, a bridge means secured tosaid base and across said slidable jaw for securing said slidable jaw onsaid base for pivotal and slidable motion relative to said stationaryjaw, said means including a steel ball under pressure in a directiontoward said base which rides in said groove in said slidable jaw, and adrive means secured to said base to impart slidable motion to saidslidable jaw as said drive means is operated.

2. An adjustable slit device as claimed in claim 1, wherein said drivemeans includes parallel worm-worm gears and a cam secured to each ofsaid worm gears rotatable therewith and positioned in contact with saidslidable jaw to impart slidable motion thereto.

3. An adjustable slit device which comprises an elongated base, astationary jaw secured at one end on the upper surface of said base, aslidable jaw slidably and pivotably mounted on the upper surface of saidbase relative to said stationary jaw, an axially extending groove in theupper surface of said slidable jaw, a bridge secured to said base acrosssaid slidable jaw, said bridge comprising a centrally located retainerhousing perpendicular to said base, a spring pressed steel ball securedunder pressure in said retainer housing, said steel ball adapted to ridein said groove in said slidable jaw to secure said slidable jaw forpivotal and slidable motion on said base relative to said stationaryjaw, drive means for imparting slidable motion to said slidable jaw,said drive means including parallel drive worms and parallel driven wormgears adapted to be driven by said drive worms, a cam secured to thesurface of each of said driven worm gears and adapted to contact saidslidable jaw to impart a slidable mot-ion thereto, and a spring meanssecured to said slidable jaw and to the base at said drive means tomaintain said slidable jaw in contact with said cam in either directionof motion.

References Cited in the file of this patent UNITED STATES PATENTS811,164 Murray Jan. 30, 1906 1,211,733 McQueen Jan. 9, 1917 2,168,215Keitel Aug. 1, 1939 2,255,933 Land Sept. 16, 1941 2,467,600 Shipley Apr.19, 1949 2,548,755 Vossberg et a1. Apr. 10, 1951 2,755,707 Meltzer July24, 1956 FOREIGN PATENTS 813,245 Great Britain May 13, 1959 821,393Great Britain Oct. 7, 1959 UNITED STATES PATENT OFFICE CERTIFICATION OFCORRECTION Patent No, 2, 998 73O September 5 1961 Nicholas M. Raskhodoffet e1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 3, line 63, for "radio" read ratio Signed and sealed this 17thday of April 1962.,

( SEAL) Attest:

ESTON. G. JOHNSON DAVID L.., LADD Commissioner of Patents AttestingOfficer

